Medicine liquid injection device where medicine liquid sucked up from medicine liquid tank and injected to subject does not flow back

ABSTRACT

The present invention provides liquid injector  100  wherein syringe  210  sucks a liquid from liquid tank  200  in a suck state in which connection switch mechanism  105  connects syringe tube  103  to tank tube  102 , and syringe  210  injects the liquid into a patient in an injection state in which connection switch mechanism  105  connects syringe tube  103  to patient tube  101 . Since connection switch mechanism  105  blocks patient tube  101  in the suck state, the liquid does not flow back into syringe  210  from the patient. Since tank tube  102  is blocked in the injection state, the liquid does not flow back into liquid tank  200  from syringe  210 . Therefore, it is possible to provide liquid injector  100  capable of preventing a backflow of the liquid from the patient to syringe  210  or liquid tank  200  in the structure in which syringe  210  sucks and injects the liquid from liquid tank  200  into the patient.

This application is the U.S. National Phase under 35 U.S.C. §371 ofInternational Application PCT/JP2003/009972, filed Aug. 6, 2003, whichclaims priority to Japanese Patent Application No. 2002-231160, filedAug. 8, 2002. The International Application was not published under PCTArticle 21(2) in English

TECHNICAL FIELD

The present invention relates to a liquid injector for injecting aliquid into a patient, and more particularly, to a liquid injector inwhich a syringe having a cylinder member and a piston member insertedslidably into the cylinder member is used to suck a liquid from a liquidtank and inject the liquid into a patient.

BACKGROUND ART

Currently, CT (Computed Tomography) scanners used in medical facilitiescan create cross-sectional images of a patient by the application ofX-ray imaging. MRI (Magnetic Resonance Imaging) apparatuses can createcross-sectional images of a patient in real time with the magneticresonance effect. Angiographic apparatuses can image blood vessels of apatient by the application of the X-ray imaging.

When the abovementioned apparatuses are used, a patient may be injectedwith a liquid such as a contrast medium and saline. Liquid injectors forautomatically performing the injection have been put into practical use.Such a liquid injector has an injection head on which a syringe isremovably mounted. The syringe has a cylinder member which is filledwith a liquid. A piston member is slidably inserted into the cylindermember.

Some syringe products are already filled with liquids, and other syringeproducts allow operators to add desired liquids thereinto. When such asyringe is used in a liquid injector, the syringe is connected through atank tube to a liquid tank filled with a liquid, and the syringe ismounted on an injection head, by way of example. The injection headseparately holds a cylinder member and a piston member of the syringeand moves the piston member rearward from the cylinder member with aslider mechanism.

After the liquid is added into the syringe from the liquid tank, theliquid tank and the tank tube are removed from the syringe which, inturn, is connected to a patient through a patient tube. In this state,the injection heads moves the piston member forward into the cylindermember with the slider mechanism to inject the liquid from the syringeinto the patient.

In the conventional liquid injector, however, an operator needs toconnect the syringe to the liquid tank through the tank tube when theliquid is sucked from the liquid tank into the syringe, while theoperator needs to remove the tank tube from the syringe and connect thepatient tube to the syringe when the liquid is injected into the patientfrom the syringe. This requires complicated operation by the operatorand thus raises the concern that the operator might contaminate the tanktube or patient tube.

To solve the abovementioned problem, another liquid injector has asyringe tube connected to a syringe, a tank tube connected to a liquidtank, and a patient tube connected to a patient, in which those tubesare connected through a switching valve. In the liquid injector, aliquid is sucked from the liquid tank into the syringe while theswitching valve is manually operated to block the patient tube andconnect the tank tube to the syringe tube.

Then, the liquid is injected into the patient from the syringe while theswitching valve is manually operated to block the tank tube and connectthe patient tube to the syringe tube. In such a liquid injector, since aliquid can be added into a small-capacity syringe from a large-capacityliquid tank, the liquid can be injected into a plurality of patientsonly by replacing the patient tube with another one.

In the abovementioned liquid injector, however, the operation iscomplicated since an operator needs to operate manually the switchingvalve. This may lead to erroneous operation, for example, the operatorattempting to inject the liquid into the patient from the syringe whilethe patient tube is blocked and the tank tube is connected to thesyringe tube, or the operator attempting to suck the liquid from theliquid tank into the syringe while the tank tube is blocked and thepatient tube is connected to the syringe tube.

To solve the problem, the applicants have proposed a liquid injectorwhich has a syringe tube connected to a syringe, a tank tube connectedto a liquid tank, and a patient tube connected to a patient, in whichthose tubes are connected through a tube connecting means and a one-wayvalve is provided for each of the tank tube and the patient tube.

In the liquid injector, when an injection head moves a piston memberrearward from a cylinder member, the one-way valve for the patient tubeis closed and the one-way valve for the tank tube is opened, so that aliquid is sucked from the liquid tank into the syringe. On the otherhand, when the injection head moves the piston member forward into thecylinder member, the one-way valve for the tank tube is closed and theone-way valve for the patient tube is opened, so that the liquid isinjected into the patient from the liquid.

In the liquid injector, contamination can be prevented only by replacingthe patient tube with another one for each patient, and a large amountof liquid in the liquid tank can be injected into patients through thesyringe.

In reality, however, the one-way valve is formed in structure to beclosed by a backflow of the liquid, so that a slight amount of blood orliquid may flow back into the syringe from the patient and then into theliquid tank from the syringe in the abovementioned liquid injector. Inthis case, the syringe and the liquid injector are contaminated, whichmeans that the liquid cannot be injected into a plurality of patientseven when a large-capacity liquid tank is used.

DISCLOSURE OF INVENTION

The present invention has been made in view of the abovementionedproblems, and it is an object of the present invention to provide aliquid injector capable of using a syringe to suck a liquid from aliquid tank and inject the liquid into a patient, and preventing theliquid or blood from flowing back into the syringe or the liquid tankfrom the patient.

A liquid injector according to the present invention has a patient tube,a syringe tube, a tank tube, a tube connecting means, a syringe drivemechanism, a connection switch mechanism, and an interlock controlmeans. A syringe having a cylinder member and a piston member slidablyinserted into the cylinder member is used to suck a liquid from a liquidtank and inject the liquid into a patient.

The patient tube has a leading end connected to the patient, while thesyringe tube has a trailing end connected to the syringe. The tank tubehas a trailing end connected to the liquid tank. The tube connectingmeans connects the trailing end of the patient, the leading end of thesyringe tube, and the leading end of the tank tube. The syringe drivemechanism relatively moves the cylinder member and/or the piston memberto cause the syringe to suck and inject the liquid. The connectionswitch mechanism switches between a suck state in which the patient tubeis blocked and the syringe tube is connected to the tank tube and aninjection state in which the tank tube is blocked and the syringe tubeis connected to the patient tube. The interlock control means interlocksthe operation of the syringe drive mechanism and the operation of theconnection switch mechanism.

Thus, in the liquid injector of the present invention, the syringe drivemechanism causes the syringe to suck the liquid from the liquid tank inthe suck state in which the connection switch mechanism connects thesyringe tube to the tank tube, and the syringe drive mechanism causesthe syringe to inject the liquid into the patient in the injection statein which the connection switch mechanism connects the syringe tube tothe patient tube. Since the connection switch mechanism blocks thepatient tube in the suck state, the liquid or blood does not flow backfrom the patient into the syringe. Since the tank tube is blocked in theinjection state, the liquid or the like does not flow back from thesyringe into the liquid tank.

Consequently, contamination of the liquid in the syringe and the liquidtank can be prevented, and the liquid can be injected into a number ofpatients in turn only by replacing the patient tube with another onewithout replacing the liquid tank or the syringe, for example.

Various means referred to in the present invention may be any as long asit is formed to realize the function, and for example, can be realizedas dedicated hardware which performs a predetermined function, a dataprocessing apparatus which has a predetermined function provided by acomputer program, a predetermined function realized inside a dataprocessing apparatus by a computer program, a combination thereof, andthe like.

Various components referred to in the present invention do not need tobe independent items, and it is possible that a plurality of componentsis formed as one member, a component is contained as part of anothercomponent, and a component shares a portion with another component.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the general structure of a liquidinjector of Embodiment 1 according to the present invention.

FIG. 2 is a front view showing the outer appearance of the front of aconnection switch mechanism.

FIG. 3 is a perspective view showing the outer appearance of the frontof the connection switch mechanism.

FIG. 4 is a perspective view showing the outer appearance of the back ofthe connection switch mechanism.

FIG. 5 is a block diagram showing the circuit configuration of theliquid injector.

FIG. 6 is a flow chart showing a method of injecting a liquid with theliquid injector.

FIGS. 7 a and 7 b are front views showing the outer appearance of thefront of a connection switch mechanism in a first variation.

FIGS. 8 a and 8 b are perspective views showing the outer appearance ofa connection switch mechanism in a second variation.

FIG. 9 is a front view showing the outer appearance of the back of theconnection switch mechanism in the second variation.

FIG. 10 is a front view showing the outer appearance of a needle.

FIG. 11 is a schematic diagram showing the general structure of a liquidinjector of Embodiment 2.

FIG. 12 is a front view showing the outer appearance of the front of aconnection switch mechanism of the liquid injector of Embodiment 2.

FIG. 13 is a perspective view showing the outer appearance of the frontof the connection switch mechanism.

FIG. 14 is a perspective view showing the outer appearance of the backof the connection switch mechanism.

BEST MODE FOR CARRYING OUT THE INVENTION Configuration of Embodiment 1

Embodiment 1 of the present invention is hereinafter described withreference to FIGS. 1 to 6. Liquid injector 100 in Embodiment 1 haspatient tube 101, tank tube 102, syringe tube 103, tube connectingmember 104 serving as a tube connecting means, a syringe drive mechanism(not shown), connection switch mechanism 105, integrative controlcircuit 106 serving as an interlock control means, operation panel 107,liquid crystal display 108, and the like. As shown in FIG. 1, thetrailing end of the patient tube 101, the leading end of the syringetube 103, and the leading end of the tank tube 102 are connected throughtube connecting member 104.

Patient tube 101 is formed of resin tube 111, one-way valve 112,connector 113, and catheter 114, in order from the trailing end to theleading end. Catheter 114 at the leading end is removably connected to apatient (not shown). Resin tube 111 is made, for example, ofpolyurethane tube containing nylon mesh, and catheter 114 is removablyconnected to the leading end thereof through connector 113. One-wayvalve 112 is provided at a position near the leading end of resin tube111 to regulate the movement of constant medium C serving as a liquid inthe direction from resin tube 111 to catheter 114.

Tank tube 102 is formed of resin tube 116 and connector 117 in orderfrom the leading end to the trailing end. Resin tube 116 is also made ofpolyurethane tube containing nylon mesh, and liquid tank 200 isremovably connected to connector 117 at the trailing end. Liquid tank200 is formed to have a larger capacity than syringe 210 and containscontrast medium C in advance.

Syringe tube 103 is formed of resin tube 119 and connector 120 in orderfrom the leading end to the trailing end. Syringe 210 is removablyconnected to connector 120 at the trailing end. Syringe 210 is formed ofcylinder member 211 and piston member 212 which is slidably insertedinto cylinder member 211.

As shown in FIG. 5, the syringe drive mechanism has syringe drive motor122, empty sensor 123, and full sensor 124. Syringe 210 connected tosyringe tube 103 is removably mounted on the syringe drive mechanism(not shown). The syringe drive mechanism uses syringe drive motor 122 asa drive source to move piston member 212 of syringe 210 while holdingcylinder member 211, thereby causing syringe 210 to suck and injectcontrast medium C.

Empty sensor 123 senses piston member 212 moving to the leading end ofcylinder member 211 to recognize that contrast medium C is not containedin syringe 210. Full sensor 124 senses piston member 212 moving to thetrailing end of cylinder member 211 to recognize that contrast medium Cis contained in syringe 210 to its full capacity.

As shown in FIGS. 2 to 4, connection switch mechanism 105 has body panel130, injection block mechanism 131, suck block mechanism 132, open orclose interlock mechanism 133 and the like. Injection block mechanism131 is formed of injection press member 135 and injection hold member136. Suck block mechanism 132 is formed of suck press member 137 andsuck hold member 138. Open or close interlock mechanism 133 is formed ofconnection switch motor 140 realized, for example by a stepping motor,gear train 141, and press pivot member 142, in which connection switchmotor 140 pivotally supports press pivot member 142 through gear train141.

Injection press member 135 and suck press member 137 are formed to beintegral with press pivot member 142. Injection press member 135 ismovably disposed at a position where it presses patient tube 101 whenpress pivot member 142 is normally rotated. Suck press member 137 ismovably disposed at a position where it presses tank tube 102 when presspivot member 142 is reversely rotated.

Injection hold member 136 is disposed opposite to injection press member135 through patient tube 101, while suck hold member 138 is disposedopposite to suck press member 137 through tank tube 102. Connectionswitch mechanism 105 switches between a suck state in which patient tube101 is blocked and syringe tube 103 is connected to tank tube 102 and aninjection state in which tank tube 102 is blocked and syringe tube 103is connected to patient tube 101.

Portions of injection and suck press members 135, 137 for pressing tubes101, 102, respectively, are formed on convex surfaces which are curvedcylindrically. Portions of injection and suck hold members 136, 138 forpressing tubes 101, 102, respectively, are formed on concave surfaceswhich are curved cylindrically.

Gear train 141 is formed of pinion gear 144 connected directly toconnection switch motor 140 and spur gear 145 connected directly topress pivot member 142. Convex 146 is formed on spur gear 145. Injectionblock sensor 148 realized by a photosensor is disposed at a position forsensing convex 146 in the suck state. Suck block sensor 149 realized bya photosensor is disposed at a position for sensing convex 146 in theinjection state. Thus, injection block sensor 148 senses the blocking ofpatient tube 101, while suck block sensor 149 senses the blocking oftank tube 102.

Integrative control circuit 106 is realized by a microcomputer which hasappropriate control programs implemented as firmware. As shown in FIG.5, operation panel 107, liquid crystal display 108, syringe drive motor122, empty sensor 123, full sensor 124, connection switch motor 140,injection block sensor 148, suck block sensor 149 and the like areconnected to integrative control circuit 106.

Although details are described later, integrative control circuit 106displays various types of data on liquid crystal display 108 andintegrally controls the operation of respective motors 122, 140 inresponse to data input to operation panel 107 or signals of respectivesensors 123, 124, 148, and 149.

Integrative control circuit 106 drives syringe drive motor 122 to suckcontrast medium C from liquid tank 200 into syringe 210 after injectionblock sensor 148 senses the blocking of patient tube 101, and drivessyringe drive motor 122 to inject contrast medium C into the patientfrom syringe 210 after suck block sensor 149 senses the blocking of tanktube 102.

Operation of Embodiment 1

In the configuration as described above, liquid injector 100 ofEmbodiment 1 is used, for example, to inject contrast medium C servingas the liquid into a patient whose images are created with a CT scanneror an MRI apparatus. In this case, an operator connects patient tube 101to the patient and connects tank tube 102 to liquid tank 200. Inaddition, the operator connects syringe tube 103 to syringe 210 which isthen loaded on the syringe drive mechanism.

In liquid injector 100 of Embodiment 1, when a patient who is injectedwith contrast medium C is changed, only catheter 114 of patient tube 101needs to be changed for each patient while liquid tank 200 and syringe210 are connected to tank tube 102 and syringe tube 103, respectively,without any change.

As shown in FIG. 6, in liquid injector 100 of Embodiment 1, connectionswitch motor 140 is normally rotated in an initial state until injectionblock sensor 148 senses the blocking of patient tube 101 (steps S1, S2),thereby blocking patient tube 101.

In this state, when the operator who connected patient tube 101 to thepatient makes input to operation panel 107 for sucking or injectingcontrast medium C (step S3 or S8), liquid injector 100 performs suckoperation or injection operation in response to the input.

For example, when the input is made for sucking (step S3), syringe drivemotor 122 is driven to move piston member 212 of syringe 210 rearwardfrom cylinder member 211 while patient tube 101 is blocked as describedabove (steps S1, S2), and thus contrast medium C is sucked from liquidtank 200 into syringe 210 (step S6).

When full sensor 124 senses piston member 212 being moved rearward tothe trailing end (step S5), the drive of syringe drive motor 122 isstopped to terminate the sucking operation of contrast medium C (stepS7). Contrast medium C is automatically sucked into syringe 210 to itsfull capacity.

When the operator who is checking the abovementioned sucking operationmakes input to operation panel 107 for stopping the sucking in progressas desired (step S5), however, the drive of syringe drive motor 122 isstopped to terminate the sucking operation of contrast medium C (stepS7). In this case, an amount of contrast medium C desired by theoperator is sucked into syringe 210.

When input is made to perform injection with contrast medium C containedin syringe 210 as described above (step S8), connection switch motor 140is reversely rotated until suck block sensor 149 senses the blocking oftank tube 102 (steps S9, S10). In this manner, patient tube 101 isopened and tank tube 102 is blocked.

After the blocking is completed, syringe drive motor 122 is driven tomove piston member 212 of syringe 210 forward to inject contrast mediumC into the patient from syringe 210 (step S13). When empty sensor 123senses piston member 212 being moved forward to the leading end (stepS11), the drive of syringe drive motor 122 is stopped to terminate theinjection operation of contrast medium C (step S14). All of contrastmedium C in syringe 210 is automatically injected into the patient.

When the operator who is checking the abovementioned injection operationmakes input to operation panel 107 for stopping the injection inprogress as desired (step S12), however, the drive of syringe drivemotor 122 is stopped to terminate the injection operation of contrastmedium C (step S14). In this case, an amount of contrast medium Cdesired by the operator is injected into the patient. After theinjection of contrast medium C is completed as described above,connection switch motor 140 is normally rotated until injection blocksensor 148 senses the blocking of patient tube 101 as describedabove(steps S1, S2), and patient tube 101 is blocked.

Effect of Embodiment 1

In liquid injector 100 of Embodiment 1, since patient tube 101 isreliably blocked by injection block mechanism 131 in the suck state inwhich contrast medium C is sucked from liquid tank 200 into syringe 210,a backflow of contrast medium C or blood from the patient into syringe210 can be prevented. In addition, since tank tube 102 is reliablyblocked by suck block mechanism 132 in the injection state in whichcontrast medium C is injected into the patient from syringe 210, abackflow of contrast medium C or the like from syringe 210 into liquidtank 200 can be prevented.

It is thus possible to prevent the contamination of contrast medium C insyringe 210 and liquid tank 200. Contrast medium C can be injected intoa number of patients in turn only by replacing catheter 114 of patienttube 101 without replacing liquid tank 200 or syringe 210.

Particularly, in liquid injector 100 of Embodiment 1, the operation ofinjection block mechanism 131 is interlocked with the operation of thesyringe drive mechanism, thereby eliminating erroneous operation, forexample, the operator attempting to inject the liquid into the patientfrom the syringe while patient tube 101 is blocked and tank tube 102 isconnected to syringe tube 103, or the operator attempting to suck theliquid from liquid tank 200 into syringe 210 while tank tube 102 isblocked and patient tube 101 is connected to syringe tube 103.

In liquid injector 100 of Embodiment 1, injection block mechanism 131for blocking patient tube 101 and suck block mechanism 132 for blockingtank tube 102 are formed on one press pivot member 142, so that both ofpatient tube 101 and tank tube 102 are not blocked or opened.

In liquid injector 100 of Embodiment 1, catheter 114 is connected toresin tube 111 through connector 113 and is easily replaced. Inaddition, one-way valve 112 is provided at the position near the leadingend of resin tube 111, which can prevent a backflow of contrast medium Cor blood more reliably.

Since patient tube 101 is automatically blocked by injection blockmechanism 131 upon completion of the injection of contrast medium C intothe patient from syringe 210, contrast medium C or blood can beprevented from flowing back at all times. Also, since respective tubes101, 102 are blocked by injection and suck press members 135, 137 andinjection and suck hold members 136, 138 with their convex surfaces andconcave surfaces on the cylinders, respectively, a backflow of contrastmedium C or blood can be prevented more reliably.

In liquid injector 100 of Embodiment 1, one press pivot member 142 ispivoted to switch between the suck state in which patient tube 101 isblocked and the injection state in which tank tube 102 is blocked, whichcan ensure the switching between the suck state and the injection statewith the simple structure.

In liquid injector 100 of Embodiment 1, since connection switch motor140 for pivoting press pivot member 142 is realized by a stepping motor,press pivot member 142 can be pivoted at a predetermined angle andstopped there. This can reliably maintain the suck state and theinjection state with the simple structure.

Variations of Embodiment 1

The present invention is not limited in any way to the abovementionedembodiment, and permits a number of variations without departing fromthe scope and spirit thereof. For example, while Embodiment 1 has shownpatient tube 101, syringe tube 103, and tank tube 102 connected throughtube connecting member 104 separate from those tubes, it is possible toform patient tube 101, syringe tube 103, tank tube 102, and tubeconnecting member 104 as an integral part.

While Embodiment 1 has shown that the portions of injection and suckpress members 135, 137 and injection and suck hold members 136, 138 forblocking respective tubes 101, 102 are formed of the convex surfaces andthe concave surfaces on the cylinders, they can be planes or S-shapedportions.

In Embodiment 1, one-way valve 112 is provided for patient tube 101 toreliably prevent a backflow of contrast medium C or blood. However, itcan be omitted, and a one-way valve (not shown) for regulating themovement of contrast medium C in the direction from liquid tank 200 tosyringe 210 can be provided for tank tube 102.

Embodiment 1 has shown connection switch motor 140 realized by thestepping motor to stop press pivot member 142 at a predetermined angle.Alternatively, a lock mechanism (not shown) can be connected toconnection switch motor 140 realized by a supersonic motor or the liketo stop press pivot member 142 at a predetermined angle, for example.

In connection switch mechanism 105 of Embodiment 1, injection pressmember 135 of injection block mechanism 131 and suck press member 137 ofsuck block mechanism 132 are formed to be integral with press pivotmember 142 of open or close interlock mechanism 133. However, as inconnection switch mechanism 150 shown in FIGS. 7 a and 7 b, it ispossible to slidably support injection press member 151 and suck pressmember 152 with a guide rail (not shown) or the like and connect them tocrank member 154 of open or close interlock mechanism 153 throughinjection link member 155 and suck link member 156.

Embodiment 1 has shown that convex 146 of spur gear 145 of open or closeinterlock mechanism 133 is sensed by injection block sensor 148 and suckblock sensor 149. However, as in connection switch mechanism 150 shownin FIGS. 7 a and 7 b, convex 157 of crank member 154 can be sensed byinjection block sensor 158 and suck block sensor 159 which are realizedby mechanical switches.

In addition, as in connection switch mechanism 160 shown in FIGS. 8 a, 8b, and 9, it is possible that injection press member 161 and suck pressmember 162 are supported slidably in the same direction to faceinjection hold member 163 and suck hold member 164, respectively, and toengage with a surface of rotatable cam member 167 of open or closeinterlock mechanism 166, on which concaves and convexes are formed.

It is also possible that convex 168 of cam member 167 is sensed byinjection block sensor 148 and suck block sensor 149, or convexes 169,170 of injection press member 161 and suck press member 162 are senseddirectly by injection block sensor 148 and suck block sensor 149 as inconnection switch mechanism 160.

While Embodiment 1 has shown that connection switch motor 140 isrealized by the stepping motor to maintain the suck state and theinjection state, the suck state and the injection state can bemaintained by forming gear train 172 of worm gears as in connectionswitch mechanism 160 shown in FIGS. 8 a, 8 b, and 9.

In connection switch mechanism 160, the trailing ends of injection andsuck press members 161, 162 are positioned at concave 173 of the surfaceof cam member 167 to release the blocking of respective tubes 101, 102,respectively. Thus, after one of them is completely blocked, theblocking of the other can be released, so that a backflow of contrastmedium C or the like can be prevented without fail.

In addition, since concave 174 at which both of injection and suck pressmembers 161, 162 are simultaneously located is also formed on cam member167 in connection switch mechanism 160, the blocking of respective tubes101, 102 can be released simultaneously as desired, and respective tubes101, 102 can be easily loaded.

To ensure such operation, convexes 169, 170 of injection press member161 and suck press member 162 are preferably sensed directly byinjection block sensor 148 and suck block sensor 149 described above.However, it is possible to provide dedicated release sensor 176 forsensing both of injection and suck press members 161, 162 beingpositioned in concave 174.

While Embodiment 1 has shown that the leading end of patient tube 101 isformed of catheter 114, it can be formed of butterfly needle 178 asshown in FIG. 10. Particularly, in liquid injector 100 of Embodiment 1,catheter 114 of patient tube 101 is connected to resin tube 111 throughconnector 113, it can be replaceable with butterfly needle 178.

While Embodiment 1 has shown the liquid realized by contrast medium C,it can be a drug or saline. It is also possible that contrast medium Cand saline W can be freely injected as in liquid injector 300 shown inFIG. 11.

Configuration of Embodiment 2

Liquid injector 300 described above is hereinafter described briefly asEmbodiment 2 with reference to FIG. 11. In liquid injector 300 ofEmbodiment 2, saline W which is a solution with lower viscosity thancontrast medium C is contained in solution tank 301 which is connectedto the trailing end of attachment tube 302.

The leading end of attachment tube 302 is connected to resin tube 111 ofpatient tube 101 through tube connecting member 303 serving as a tubeattaching means. Injection block mechanism 131 is positioned betweentube connecting members 104, 303 on resin tube 111.

Roller pump 302 serving as a solution injection device and attachmentblock mechanism 305 are positioned in order from the trailing end to theleading end of attachment tube 302. They are also connected tointegrative control circuit 106 (not shown). Roller pump 304 injectssaline W in solution tank 301 into a patient. Attachment block mechanism305 presses and blocks attachment tube 302 to freely open or closeattachment tube 302. Integrative control circuit 106 causes attachmentblock mechanism 305 to release the blocking only when connection switchmechanism 105 blocks patient tube 101, and causes roller pump 304 tooperate only when the blocking by attachment block mechanism 305 isreleased.

Operation of Embodiment 2

In liquid injector 300 of Embodiment 2, contrast medium C and saline Wcan be freely injected into the patient. Specifically, the blocking byAttachment block mechanism 305 is released and roller pump 304 isoperated only when connection switch mechanism 105 blocks patient tube101.

Effect of Embodiment 2

As a result, in liquid injector 300 of Embodiment 2, contrast medium C,saline W, or blood does not flow back from the patient into solutiontank 301 and liquid tank 200, saline W does not move into liquid tank200 from solution tank 301, or contrast medium C does not move intosolution tank 301 from liquid tank 200 or syringe 210.

Variations of Embodiment 2

While Embodiment 2 has shown the structure in which the leading end ofattachment tube 302 is connected at the position between the leading endof patient tube 101 and injection block mechanism 131, it is possiblethat the leading end of attachment tube 302 is connected to a positionbetween injection block mechanism 131 on patient tube 101 and tubeconnecting member 104, for example.

It is also possible that a second injection block mechanism (not shown)is additionally provided at a position between the leading end ofpatient tube 101 and tube connecting member 303. In the structure,roller pump 304 can be omitted to suck and inject saline W with syringe210.

Configuration of Embodiment 3

Embodiment 3 of the present invention is hereinafter described brieflywith reference to FIGS. 12 to 14. In a liquid injector (not shown) ofEmbodiment 3, connection switch mechanism 401 is formed of injectionblock mechanism 402 and switching valve 403 which is provided at theposition of tube connecting member 104.

Injection press member 152 of injection block mechanism 402 is connectedto connection switch motor 140 with rack and pinion mechanism 404. Aswitch sensor (not shown) is connected to switching valve 403. Theswitch sensor is connected to integrative control circuit 106 (notshown) which integrally controls the respective parts in accordance withoutput from the switch sensor.

Operation of Embodiment 3

In the liquid injector of Embodiment 3, when an operator manuallyoperates switching valve 403 as desired, switching valve 403 switchesbetween the suck state and the injection state, and the switch operationof switching valve 403 is sensed by the switch sensor and thenrecognized by integrative control circuit 106.

Integrative control circuit 106 causes injection block mechanism 402 toblock patient tube 101 to permit the suck operation of a syringe drivemechanism when switching valve 403 is switched to the suck state. Whenswitching valve 403 is switched to the injection state, integrativecontrol circuit 106 causes injection block mechanism 402 to open patienttube 101 to permit the injection operation of the syringe drivemechanism.

Effect of Embodiment 3

In the liquid injector of Embodiment 3, switching valve 403 is manuallyoperated to integrally control the respective parts such as injectionblock mechanism 402 to set switching between the suck state and theinjection state, so that the switching between the suck state andinjection state can be reliably achieved with intuitively recognizableand simple operation.

Variations of Embodiment 3

While Embodiment 3 has shown that switching valve 403 is used as theoperation switch to interlock the operation of injection block mechanism402 and the like, it is possible that a drive motor (not shown) isconnected to switching valve 403, and a separate operation switch ismanually operated to interlock the operation of switching valve 403 andthe operation of injection block mechanism 402, for example.

1. A liquid injector for causing a syringe to suck a liquid from aliquid tank and inject the liquid into a patient, the syringe having acylinder member and a piston member inserted slidably into the cylindermember, comprising: a patient tube having a leading end connected to thepatient; a syringe tube having a trailing end connected to the syringe;a tank tube having a trailing end connected to the liquid tank; a tubeconnecting means for connecting a trailing end of the patient tube, aleading end of the syringe tube, and a leading end of the tank tube; asyringe drive mechanism for relatively moving the cylinder member and/orthe piston member to cause the syringe to suck and inject the liquid; aconnection switch mechanism for switching between a suck state in whichthe patient tube is blocked and the syringe tube is connected to thetank tube and an injection state in which the tank tube is blocked andthe syringe tube is connected to the patient tube; an interlock controlmeans for interlocking operation of the syringe drive mechanism andoperation of the connection switch mechanism; and an attachment tubehaving a trailing end connected to a solution injector for injecting asolution into the patient, tube attaching means for attaching a leadingend of the attachment tube to the patient tube, and an attachment blockmechanism for pressing and blocking the attachment tube to freely openor close the attachment tube, wherein the interlock control means causesthe attachment block mechanism to release the blocking only when theconnection switch mechanism blocks the patient tube.
 2. The liquidinjector according to claim 1, wherein the connection switch mechanismhas an injection block mechanism for pressing the patient tube to freelyopen or close the patient tube.
 3. The liquid injector according toclaim 2, wherein the connection switch mechanism also has a switchingvalve provided at the position of the tube connecting means.
 4. Theliquid injector according to claim 2, wherein the connection switchmechanism also has a suck block mechanism for pressing the tank tube tofreely open or close the tank tube.
 5. The liquid injector according toclaim 4, wherein the connection switch mechanism also has an open orclose interlock mechanism for interlocking open and close operation ofthe injection block mechanism and the suck block mechanism such that oneof them performs open operation when the other performs close operation.6. The liquid injector according to claim 5, wherein the injection blockmechanism has an injection press member movably disposed at a positionfor pressing the patient tube and an injection hold member disposedopposite to the injection press member through the patient tube, thesuck block mechanism has a suck press member movably disposed at aposition for pressing the tank tube and a suck hold member disposedopposite to the suck press member through the tank tube, and the open orclose interlock mechanism has a press pivot member having the injectionpress member and the suck press member formed integrally and supportedpivotally.
 7. The liquid injector according to claim 5, wherein theinjection block mechanism has an injection press member slidablysupported at a position for pressing the patient tube and an injectionhold member disposed opposite to the injection press member through thepatient tube, the suck block mechanism has a suck press member slidablysupported at a position for pressing the tank tube and a suck holdmember disposed opposite to the suck press member through the tank tube,and the open or close interlock mechanism has a crank member pivotallysupported on its own trailing end, an injection link member forconnecting a leading end of the crank member to the injection pressmember, and a suck link member for connecting the leading end of thecrank member to the suck press member.
 8. The liquid injector accordingto claim 5, wherein the injection block mechanism has an injection pressmember slidably supported at a position for pressing the patient tubeand an injection hold member disposed opposite to the injection pressmember through the patient tube, the suck block mechanism has a suckpress member slidably supported at a position for pressing the tank tubeand a suck hold member disposed opposite to the suck press memberthrough the tank tube, and the open or close interlock mechanism has acam member pivotally supported and having a concave and a convex withwhich the injection press member and the suck press member engage. 9.The liquid injector according to claim 2, wherein the interlock controlmeans causes the injection block mechanism to block the patient tubewhen the injection by the syringe drive mechanism is completed.
 10. Theliquid injector according to claim 1, further comprising an injectionblock sensor for sensing the patient tube being blocked and a suck blocksensor for sensing the tank tube being blocked, wherein the interlockcontrol means causes the syringe drive mechanism to perform the suckafter the injection block sensor senses the blocking and causes thesyringe drive mechanism to perform the injection after the suck blocksensor senses the blocking.
 11. The liquid injector according to claim1, further comprising a one-way valve for regulating the movement of theliquid from the syringe to the patient, the one-way valve being providedfor the patient tube.
 12. The liquid injector according to claim 1,further comprising a one-way valve for regulating the movement of theliquid from the liquid tank to the syringe, the one-way valve beingprovided for the tank tube.
 13. The liquid injector according to claim1, wherein the tube attaching means attaches the leading end of theattachment tube to a portion between the leading end of the patient tubeto the connection switch mechanism.